The Truth About Testosterone, Male Sex Drive, and Big Muscles

If estrogen is the force behind female mojo, its male sexual partner is testosterone, the hormone that fuels guys' sex drive, fertility, mood, and even body type. OB-GYN Lauren Streicher, MD, and Dr. Neil Goodman, chairman of the Sex Hormones and Reproductive Endocrinology Scientific Committee at the American Association of Clinical Endocrinologists, break it down to the basics.

Sex Drive

Sex Drive

Testosterone is the hormone that powers your man's sex drive (and also plays a role in yours.) In short, normal to high testosterone = horny man. But still: factors like depression and even the food your guy eats can cause dips in testosterone, and hence, sex drive.

Fertility

Fertility

You need testosterone to make sperm, and if you have a very low testosterone, you might have a decline in the quality of sperm and number of sperm, says Streicher. But, believe it or not, men with extremely low testosterone can still produce normal sperm. Testosterone is an important stimulator of sperm production, says Goodman, but even more important is FSH, the hormone that gets sperm to travel through the different stages, and LH. FSH and LH from the pituitary gland make the testes work. If the pituitary gland doesnt work, you cant make sperm.